1. Field of the Invention
The present invention relates to a motor controller for controlling the drive of a motor.
2. Description of the Related Art
As a motor controller for controlling the drive of a motor, an inverter device used for the adjustable-speed drive of an AC motor is known, for example, as disclosed in Japanese Patent Publication No. 3592144. Such an inverter device is generally provided with an overcurrent protective device for performing gate shutdown when an excess current is detected. The overcurrent protective device that performs gate shutdown in this way determines that there is abnormality if a current feedback value sent from a current-detecting device arranged in a main circuit is not less than a predetermined value, and shuts a gate, thereby preventing damage from spreading to other parts in the inverter device.
On the other hand, the overcurrent protective device disclosed in Japanese Patent Publication No. 3592144 evaluates whether or not momentary current detection means for detecting currents of two or more phases is abnormal on the basis of the current values detected by the momentary current detection means. The overcurrent protective device prohibits the operation of the inverter device if any abnormal currents are observed.